The current clean gas injector on a Novellus HDP SPEED Chamber consists of a single injector to deliver the cleaning gasses. The chamber includes a base and a ceramic dome in form of a bell jar and is adapted to receive a semiconductor wafer at one port and is used to deposit fluorinated silicate glass (FSG, a dielectric) on the wafer. It also gets everywhere in the chamber including the inside of the ceramic dome and chamber walls. The system has an in-situ cleaning system that sends NF3 gas through a single clean gas injector to clean the chamber of the FSG.
The chamber and some walls are cleaned unevenly in this Novellas HDP SPEED Chamber system as illustrated in FIG. 1. Referring to the sketch of FIG. 1 the chamber system 10 includes the dome or bell jar over the chamber base 11. The wafer sits on an electrostatic chuck (ESC) and is held down via electrostatic forces that act on the wafer. A single injector 13 enters the base 11 of the chamber 10 at the same end as the vacuum pump port 15. The cleaning gas flows through the injector and flows into the dome as illustrated by arrow 16. The vacuum port 15 is at the same end of the chamber 10 as the injector 13. The flow of the gas is illustrated by arrow 16. The flow is up from the injector 13 opening into the dome 12 an evacuated down through the vacuum port 15. The gas flow is mostly in the direction of the arrow 16 so that the clean gas flow is mostly on the injector and the vacuum end of the chamber 10. The result is an uneven cleaning rate of the reactor chamber 10 including base and chamber walls including the dome. The uneven rate of cleaning causes buildup of aluminum fluoride in the chamber and presents particle problem for deposition. It also results in over etching on the reactor and dome walls near the injector end. It is desirable to improve the in-situ cleaning of the Novellus HDP SPEED Chamber and similar chambers.
Novellus has developed a system that is called “Toggle Clean.” Toggle Clean has two injector that enter the reactor from orifices in the floor of reactor. The purpose of these injectors is to alternate gas flow through them so that deposition in the injector tubes is cleaned. The new design flow gasses through multiple (3+) clean injectors simultaneously, providing more uniform gas flow and allowing a more robust clean.